Lumber, in particular round timber, which is intended for the generation of high-grade chips, is frequently supplied to the processing plants in lengths which are equivalent to the maximum allowable loading width of the transportation vehicles, in other words between about 2.40 m and 2.60 m long. As there are design limits to the working width of chipping machines, until now there have been virtually only two possibilities of chipping pieces of lumber of this length, that is, either by sectional chipping in so-called long log chipping machines or by previously cutting to length the pieces of lumber to match the working width of the chipping machine in question.
The first processing possibility, the sectional chipping of pieces of lumber sized to approximately the maximum allowable loading width of vehicles, can admittedly be carried out on longtimber chipping machines, on which the pieces of lumber ere cyclically fed to the chipping machine in a feeder channel provided with a conveyor belt, but considerable disadvantages have to be accepted in this operation. For instance, pieces of lumber of this relatively short length tend to lie at an angle in the long feeder channel, which not only has a disruptive effect on the chipping operation, but also impairs the degree of filling of the feed channel and so the qualitative and the quantitative capabilities of the chipping machine are unfavorable. With pieces of lumber of this length, there are consequently not only spaces at the sides in the feed channel, but also numerous gaps in the longitudinal direction as a result of the random succession of the pieces of lumber, something which not only reduces the fullness of the chipping space but also has the further disadvantage that after each chipping cycle there are a number of residual sections which drop into the empty chipping chamber during the next feed cycle and lie there unchecked in an unfavorable position for chipping. Although attempts have previously been made to counter this problem by the arrangement of a so-called displaceable baffle, this too cannot wholly prevent the occurrence of residual sections, which, if they are very narrow, (i.e., disk-shaped), and are therefore no longer caught by the pressure elements in the chipping space, can impair the quality of the chips generated quite considerably.
The second possibility of chipping pieces of lumber of this conventional transportation length is to divide them in advance into lengths which correspond to the depth of the chipping space or the working width of the chipping unit. This cutting to length of the lumber to match the working width of the cutter rotor in question is an absolute necessity in the case of disk-type chipping machines; it has, however, also already been proposed, as evidenced by U.S. Pat. No. 3,913,643, to use chipping machines with cylindrical cutter rotors. The cutting to length of the pieces of lumber has, however, the great disadvantage that the additional operating stage required for this demands a considerable structural and operational outlay and, additionally, results in a not inconsiderable loss in lumber of about 3%.